In a construction machine, a hydraulic motor is used to drive a cooling fan for cooling an engine and the like, and a hydraulic actuator is used to drive a work equipment of a dump truck, namely a body (often referred to as a hoist or a vessel), or a work equipment of a hydraulic excavator or a wheel loader. For driving the fan and the work equipment, since the usage and required characteristics thereof are different, a hydraulic circuit for driving the fan and a hydraulic circuit for driving the work equipment are generally separately provided and each hydraulic circuit has a hydraulic pump.
Since the fan is smaller in size and lighter in weight as compared with the work equipment, a small-sized hydraulic pump with a relatively small pump displacement is employed as the hydraulic pump used for driving the fan (hereinafter referred to as a fan pump). In contrast, since a relatively large amount of a hydraulic oil needs to be supplied for driving the work equipment as compared with the hydraulic motor for driving the fan, or the like, a large-sized hydraulic pump with a relatively large pump displacement is employed as the hydraulic pump for driving the work equipment (hereinafter referred to as a work equipment pump). Such a large-sized hydraulic pump requires a high production cost and a large location space. Accordingly, a size reduction of the work equipment pump has been desired.
As for the structure of the hydraulic circuit for driving the fan and the hydraulic circuit for driving the work equipment, it is known in a hydraulic excavator provided with a fan pump and a turning pump for supplying a hydraulic oil to a turning motor that turns the work equipment that a hydraulic oil flow path is switched to supply the hydraulic oil from the turning pump to a hydraulic motor for driving the fan (for instance, see Patent Document 1).    [Patent Document 1] JP-A-2007-46761